Approximately 100 simian viruses have been isolated from approximately a dozen of the some 600 recognized species of monkeys and apes. In addition, the species that have been studied harbor many viruses considered to be of human or other animal origin. The simian viruses, although generally specific for the host species, are biologic counterparts of the known animal virus families, i.e., Picornaviridae, Adenoviridae, Herpesviridae, etc. Most of these simian viruses, but particularly the herpesvirus, are capable of crossing species boundaries, sometimes with fatal results. Nonhuman primates are frequently susceptible to those animal viruses that have crossed to the simian from the human (or other animal). These viruses, likewise, may be fatal for the new host (other animal). Thus, both human and nonhuman viruses are isolated from monkeys and apes. This laboratory is unique in having the ability and physical capability to provide a complete diagnostic support for the isolation and identification of simian viruses or the serological identification of viruses or their infections. The availability of diagnostic viral reagents, appropriate biohazard containment, and some 35 years experience permits this laboratory to offer the proposed viral diagnostic support to investigators using nonhuman primates in their research and not able to obtain this same complete service elsewhere.